linux-vybrid_public/Documentation/DocBook/v4l/vidioc-subdev-g-crop.xml

<refentry id="vidioc-subdev-g-crop">
  <refmeta>
    <refentrytitle>ioctl VIDIOC_SUBDEV_G_CROP, VIDIOC_SUBDEV_S_CROP</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>VIDIOC_SUBDEV_G_CROP</refname>
    <refname>VIDIOC_SUBDEV_S_CROP</refname>
    <refpurpose>Get or set the crop rectangle on a subdev pad</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcprototype>
	<funcdef>int <function>ioctl</function></funcdef>
	<paramdef>int <parameter>fd</parameter></paramdef>
	<paramdef>int <parameter>request</parameter></paramdef>
	<paramdef>struct v4l2_subdev_crop *<parameter>argp</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
    <funcsynopsis>
      <funcprototype>
	<funcdef>int <function>ioctl</function></funcdef>
	<paramdef>int <parameter>fd</parameter></paramdef>
	<paramdef>int <parameter>request</parameter></paramdef>
	<paramdef>const struct v4l2_subdev_crop *<parameter>argp</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Arguments</title>

    <variablelist>
      <varlistentry>
	<term><parameter>fd</parameter></term>
	<listitem>
	  <para>&fd;</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>request</parameter></term>
	<listitem>
	  <para>VIDIOC_SUBDEV_G_CROP, VIDIOC_SUBDEV_S_CROP</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	  <para></para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <note>
      <title>Experimental</title>
      <para>This is an <link linkend="experimental">experimental</link>
      interface and may change in the future.</para>
    </note>

    <para>To retrieve the current crop rectangle applications set the
    <structfield>pad</structfield> field of a &v4l2-subdev-crop; to the
    desired pad number as reported by the media API and the
    <structfield>which</structfield> field to
    <constant>V4L2_SUBDEV_FORMAT_ACTIVE</constant>. They then call the
    <constant>VIDIOC_SUBDEV_G_CROP</constant> ioctl with a pointer to this
    structure. The driver fills the members of the <structfield>rect</structfield>
    field or returns &EINVAL; if the input arguments are invalid, or if cropping
    is not supported on the given pad.</para>

    <para>To change the current crop rectangle applications set both the
    <structfield>pad</structfield> and <structfield>which</structfield> fields
    and all members of the <structfield>rect</structfield> field. They then call
    the <constant>VIDIOC_SUBDEV_S_CROP</constant> ioctl with a pointer to this
    structure. The driver verifies the requested crop rectangle, adjusts it
    based on the hardware capabilities and configures the device. Upon return
    the &v4l2-subdev-crop; contains the current format as would be returned
    by a <constant>VIDIOC_SUBDEV_G_CROP</constant> call.</para>

    <para>Applications can query the device capabilities by setting the
    <structfield>which</structfield> to
    <constant>V4L2_SUBDEV_FORMAT_TRY</constant>. When set, 'try' crop
    rectangles are not applied to the device by the driver, but are mangled
    exactly as active crop rectangles and stored in the sub-device file handle.
    Two applications querying the same sub-device would thus not interact with
    each other.</para>

    <para>Drivers must not return an error solely because the requested crop
    rectangle doesn't match the device capabilities. They must instead modify
    the rectangle to match what the hardware can provide. The modified format
    should be as close as possible to the original request.</para>

    <table pgwide="1" frame="none" id="v4l2-subdev-crop">
      <title>struct <structname>v4l2_subdev_crop</structname></title>
      <tgroup cols="3">
        &cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>pad</structfield></entry>
	    <entry>Pad number as reported by the media framework.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>which</structfield></entry>
	    <entry>Crop rectangle to get or set, from
	    &v4l2-subdev-format-whence;.</entry>
	  </row>
	  <row>
	    <entry>&v4l2-rect;</entry>
	    <entry><structfield>rect</structfield></entry>
	    <entry>Crop rectangle boundaries, in pixels.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>reserved</structfield>[8]</entry>
	    <entry>Reserved for future extensions. Applications and drivers must
	    set the array to zero.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>
  </refsect1>

  <refsect1>
    &return-value;

    <variablelist>
      <varlistentry>
	<term><errorcode>EBUSY</errorcode></term>
	<listitem>
	  <para>The crop rectangle can't be changed because the pad is currently
	  busy. This can be caused, for instance, by an active video stream on
	  the pad. The ioctl must not be retried without performing another
	  action to fix the problem first. Only returned by
	  <constant>VIDIOC_SUBDEV_S_CROP</constant></para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	  <para>The &v4l2-subdev-crop; <structfield>pad</structfield>
	  references a non-existing pad, the <structfield>which</structfield>
	  field references a non-existing format, or cropping is not supported
	  on the given subdev pad.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>